There was once a man who was summoned to another world, and saved it. Of course, he became too popular there, and turned into an "isekai-normie". However, that man fell into a "trap" and was forcibly returned to his original world, and had to start over as a baby. This is the story of the way-too-fantastic ex-hero who lived as a gloomy high-schooler, as he gets summoned once again to that same other world in a very unexpected development.